Stress concentration

About: Stress concentration is a research topic. Over the lifetime, 23250 publications have been published within this topic receiving 422911 citations.

The buckling behavior of a central crack in a plate under tension

Abstract: A finite element procedure is presented for the analysis of the buckling and postbuckling behavior of cracks in plates loaded in tension. The procedure proposed is applied to the problem of the centrally cracked plate in tension where the loading direction is perpendicular to the crack faces. The results of the analysis show that the buckling deformations can cause a considerable amplification of the stress intensity around the crack tip. This effect, which is due to a redistribution of the stress field in the plate, increases with the length of the crack.

Mode I cracks subjected to large T-stresses

Abstract: There are several criteria for predicting brittle fracture in mode I and mixed mode loading. In this paper, the modified maximum tangential stress criterion originally proposed for mixed mode loading, is employed to study theoretically brittle fracture for mode I cracks. In particular, the effect of the non-singular term of stress, often known as the T-stress, on the angle of initiation of fracture and the onset of crack growth is explored. The T-stress component of the tangential stress vanishes along the crack line. Therefore, it is often postulated for linear elastic materials that the effect of T-stress on mode I brittle fracture can be ignored. However, it is shown here that the maximum tangential stress is no longer along the line of initial crack when the T-stress exceeds a critical value. Thus, a deviation in the angle of initiation of fracture can be expected for specimens having a large T-stress. It is shown that the deviation angle increases for larger values of T-stress. Theoretical results show that the apparent fracture toughness decreases significantly when a deviation in angle occurs. Earlier experimental results are used to corroborate the findings. The effect of large T-stresses is also explored for a crack specimen undergoing moderate scale yielding. The elastic-plastic investigation is conducted using finite element analysis. The finite element results reveal a similar deviation in the angle of maximum tangential stress for small to moderate scale yielding.

Limitations of pore-stress concentrations on the mechanical properties of porous materials

Abstract: Severe limitations on pore-stress concentration effects on mechanical properties are shown. First, the porosity dependence of materials with dilute porosities is not consistent with significant variations in stress concentrations with the stress state. Second, in non-dilute porosities, pore stress concentration effects are reduced due to pore-stress interactions as pore spacings decrease. Such reduction of stress concentrations is seen as supporting the concept of the minimum solid area correlating with properties in porous materials, and the similarity between the porosity dependence of mechanical properties and electrical and thermal conductivity. Finally, crack-pore interactions often limit the effects of pore-stress concentrations, e.g. due to small pore sizes. However, some effects of pore-stress concentrations may occur due to tensile failure from a few or an isolated pore, or more general porosity under compressive loading, but even in these cases pore shape-stress concentration effects are significantly mitigated.

Effects of Pore Morphology and Bone Ingrowth on Mechanical Properties of Microporous Titanium as an Orthopaedic Implant Material

Abstract: Successful bone formation which leads to functional osseointegration is determined by the local mechanical environment around bone-interfacing implants. In this work, a novel porous titanium material is developed and tested and then impact of porosity on mechanical properties as a function of bone ingrowth is studied numerically. A superplastic foaming technique is used to produce CP-Ti material with rounded, interconnected pores of 50% porosity; the pore size and morphology is particularly suitable for bone ingrowth. In order to understand the structure-property relations for this new material, a numerical simulation is performed to study the effect of the porous microstructure and bone ingrowth on the mechanical properties. Using ABAQUS, we create two-dimensional representative microstructures for fully porous samples, as well as samples with partial and full bone ingrowth. We then use the finite element method to predict the macroscopic mechanical properties of the foam, e.g., overall Young's modulus and yield stress, as well as the local stress and strain pattern of both the titanium foam and bone inclusions. The strain-stress curve, stress concentrations and stress shielding caused by the bone-implant modulus mismatch are examined for different microstructures in both elastic and plastic region. The results are compared with experimental data from the porous titanium samples. Based on the finite element predictions, bone ingrowth is predicted to dramatically reduce stress concentrations around the pores. It is shown that the morphology of the implants will influence both macroscopic properties (such as modulus) and localized behavior (such as stress concentrations). Therefore, these studies provide a methodology for the optimal design of porous titanium as an implant material.